Barriers And Panels

Placing barriers, screens, or deflectors in the noise path is an effective way of reducing noise transmission, provided that the barriers are large enough in size and depending upon whether the noise is high-frequency or low-frequency. High-frequency noise is reduced more effectively than low-frequency noise.

The effectiveness of a barrier depends on its location, its height, and its length. Figure 6.7.2 shows that the noise can follow five different paths.

First, noise follows a direct path to receivers who can see the source well over the top of the barrier. The barrier

FIG. 6.7.2 Noise paths from a source to a receiver. (Reprinted from National Cooperative Highway Research Program Report 174, 1976.)

TABLE 6.7.1 RELATION BETWEEN SOUND LEVEL REDUCTION, ENERGY, AND LOUDNESS FOR LINE SOURCES

To Reduce A-level Remove Portion Divide Loudness by dB of Energy (%) by

TABLE 6.7.1 RELATION BETWEEN SOUND LEVEL REDUCTION, ENERGY, AND LOUDNESS FOR LINE SOURCES

To Reduce A-level Remove Portion Divide Loudness by dB of Energy (%) by

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